Manufacture of alpha dyestuff of the anthraquinone series



' upon after a Patented May 17, 1932 PATENT OFFICE WILHELM MOSER, 0FRIEHEN, NEAR BASEL, SWITZERLAND, ASSIGNOR TO THE FIRM OF SOCIETY OFCHEMICAL INDUSTRY IN BASLE,

OF BASED, SWITZERLAND MANUFACTURE OF A DYESTUFF OF THE ANTHRAQUINONESERIES 7 .No Drawing. Application filed November 28, 1930, Serial No.498,914, and in Switzerland December 19,

In U. S. Patent No. 1,044,797 and in British Specifications No. 20,094of 1908 or No. 11,422 of 1911 there is described the production of avat-dyestuff dyeing blue-green by 5 sulfurizing Q-methyl-benzanthrone ora derivative thereof. According to the processes disclosed in saidspecifications the product is obtained in a satisfactory pure condition.

It has now been found that this dyestuif, which corresponds veryprobably to the formula p can be converted into an essentially morevaluable product of a high degree of purity by treating it with areducing agent in presence of an alkali and then separating theleuco-compound thus precipitated from the secondary dyestufi thatremains in solution. The leuco-compound may directly be used as acommercial product since, when being worked up further (drying or madeinto a paste), it already oxidizes. It can also be oxidized in a specialoperation.

The following example illustrates the invention, the parts being byweight Ewample British Specification No. 11,422 of 1911 or of U. S.Patent No. 1,044,797 in the form of an aqueous paste, are stirred with1500 parts of water and 800 parts of caustic soda solution of 30 percent. strength; there are added parts of sodium hydrosulfite and thewhole is heated to 0., and kept for hour at 5560 C. while stirring. Thedyestuif at first dissolves to a blue violet solution, Whereshort timethe leuco-compound of the pure dyestuif begins to separate in a finelygranular form. The separation is complete after the aforesaid timewhereupon the leuco-compound is filtered hot and 50 Washed with a coldaqueous solution of 20 parts of the dyestufli' of the example of causticsoda solution and sodium hydrosulfite. The pure leuco-compound may bedried, a dark powder with a coppery lustre being obtained, or stirredinboiling water through which air is blown, in which case there isobtained a blue-violet powder with a feeble coppery lustre. Bothproducts dye cotton fast blue-green tints which are essentially morepure and somewhat bluer than those obtainable by means of the parentmaterial.

What I claim is 2-- A manufacture of a dyestuff of the anthrav quinoneseries of a high degree of purity by treating the blue-green dyestuffdescribed in Patent No. 1,044,797 and corresponding very probably to theformula with a reducing agent in presence of an II I alkali, removingthe leuco-compound thus separated from the solution containing thesecondary dyestuif.

In witness whereof I have hereunto signed day of November, 1980.

my name this 17th WILHELM MOSEB.

